This invention relates to a signal testing system for multiple element monitoring apparatus and systems.
Various machines, systems and devices are connected to monitoring systems to provide automatic indication of the status and functioning of the monitored or operating system. The monitoring apparatus may include a suitable alarm or signal device or devices for individual components and functions of the operating systems to provide a desired visual or audible indication of the status of the components and functions to the signal devices and in particular indicate any malfunction or deviation from a selected system operation. For example, the co-pending application of John J. Deisinger et al, filed Oct. 16, 1987 and Ser. No. 07/109,707 and entitled "Water Heater Diagnostic Apparatus" discloses a unique monitor particularly applied to a hot water heating unit. The above application discloses a unique diagnostic system monitoring the various components and functions of the hot water heating control with a plurality of signaling devices shown as LED lamps for displaying the status of certain components as well as for displaying a malfunction of a component or some function of the system. The operating or service personnel can review the display panel and thus detect the status of the system as well as note any malfunction or fault which requires attention and possible service. With the use of the lamps, an accurate display is generated only if all lamps are functioning properly. Thus, if any lamp is burned out, the reliability of the display is correspondingly reduced.
Various systems have been suggested for monitoring of the display lamps. For example, conventionally a push button switch unit is provided such as disclosed in the Deisinger et al application to illuminate the lamps and monitor or detect, the state thereof. U.S. Pat. No. 4,447,801 which issued May 8, 1984 and U.S. Pat. No. 4,451,822 which issued May 29, 1984 each disclose special devices for testing the state of the plurality of display lamps in a monitoring device. In both instances, the system provides a complex display monitoring system to sequentially check each lamp unit. U.S. Pat. No. 4,447,801 discloses a system wherein all lamps are turned on when a main switch is turned on and then the lamps are individually tested. U.S. Pat. No. 4,451,822 suggests that a system which turns on all lamps at once has certain disadvantages and discloses a system to only sequentially check the individual lamps.
There is a need for a simple test circuit permitting selective checking of the lamps under different conditions such as on power up but in addition under other operating conditions such as a demand for a water heating cycle.